Patients undergoing surgery requiring temporary or permanent implantation of devices, such as bioabsorbable interference screws or microcell implants, catheters, leads, pacemakers, defibrillators and stents, among many others, are often subjected to implant failure associated with functional problems, for example, the technical capability of the implanted device to adhere to the human tissue and/or bone.
Implants or screws are often used to provide an “interference fit” between tissue and/or bone, in which case tolerances are necessarily tight. In the case of threaded interference screws, for example, substantial torque may be required for insertion. If the screws are formed of non-metal substances, such as PLLA (Poly-(L-Lactic Acid)) or a tricalcium phosphate/hydroxylapatite composite, the socket provided in the screw may strip upon insertion. Accordingly, it would be desirable to lubricate the screw prior to insertion, but only temporarily, so that the screw will not slip within the body after insertion. Additionally, it would be desirable to provide a growth enhancing substance on the screw to accelerate the growth of surrounding bone to the screw, and ultimately, increasing the absorption of the screw by the body. Likewise, it would be desirable to increase the lubricity of a graft during insertion and to promote cell growth between the graft and adjacent bone or tissue.
Hyaluronic acid is a naturally-occurring polysaccharide containing alternating N-acetyl-D-glucosamine and D-glucuronic acid monosaccharide units linked with beta 1-4 bonds and the disaccharide units linked with beta 1-3 glycoside bonds. Hyaluronic acid occurs usually as the sodium salt and has a molecular weight range of about 50,000 to 8×106. Hyaluronic acid is a natural lubricant which breaks down after about 18 hours.
Recently, numerous clinical studies have demonstrated the efficacy and safety of the hyaluronic acid in the treatment of osteoarthritis of the knee and other large joints, particularly for traumatic and degenerative joint diseases. Hyaluronic acid has been shown to increase cellular density, thereby promoting healing of tissue.